It is known to measure temperature using a variety of types of sensors, such as thermocouples and thermistors. It is also known to measure pressure using a variety of types of pressure sensors. In one type of pressure sensor, a diaphragm, which is under the influence of the pressure to be measured, actuates a beam bearing semiconductor strain gages. The beam and diaphragm are designed so that the strain in the beam is proportional to the pressure.
It is also known to place these strain gages in a Wheatstone bridge circuit. Compensation networks, such as thermistor-resistor combination compensation networks, have also been provided. These allow for uniform responses among sensors, and for temperature correction of the cells. Prior art sensors and circuitry are discussed in U.S. Pat. No. 4,327,350, entitled Pressure Transducer and U.S. Pat. No. 4,368,575 entitled Pressure Transducer-Method of Making Same. The contents of these patents are herein incorporated by reference.
The ideal gas equation: EQU PV=mRt
relates pressure (P) and volume (V) to the mass of a gas (m), which can be expressed in terms of a mole number (n), the gas constant (R), and absolute temperature (T). This equation can be used to determine the mass of a gas for a given pressure, volume, and temperature, for "ideal" gases. Where the behavior of a gas is non-ideal, the Van der Waal equation: EQU (P+(n.sup.2 a/V.sup.2)) (V-bn)=RTn
may be used to calculate the quantity of a substance for a given volume, pressure and temperature.